The present invention relates to a novel lubricating oil composition. More specifically, the present invention relates to a lubricating oil composition having excellent antiwear properties and friction-reducing properties, capable of maintaining the friction-reducing properties, for a prolonged period of time, useful as a lubricating oil for internal-combustion engines, automatic transmission gearboxes, dampers, power steering units and the like, particularly useful as a lubricating oil for internal-combustion engines.